Energetic materials such as thermite are presently used when highly exothermic reactions are needed. Uses include cutting, welding, purification of metal ores, and enhancing the effects of high explosives. A thermite reaction occurs between a metal oxide and a reducing metal. Examples of metal oxides include La2O3, AgO, ThO2, SrO, ZrO2, UO2, BaO, CeO2, B2O3, SiO2, V2O5, Ta2O5, NiO, Ni2O3, Cr2O3, MoO3, P2O5, SnO2, WO2, WO3, Fe3O4, CoO, Co3O4, Sb2O3, PbO, Fe2O3, Bi2O3, MnO2, Cu2O, and CuO. Example reducing metals include Al, Zr, Th, Ca, Mg, U, B, Ce, Be, Ti, Ta, Hf, and La. The reducing metal may also be in the form of an alloy or intermetallic compound of the above-listed metals.
An example of the use of thermite to enhance high explosives is U.S. Pat. No. 7,955,451 disclosing energetic thin-film-based reactive fragmentation weapons. The weapons include conventional high explosives with reactive fragments mixed within the high explosives. The reactive fragments are made by alternating layers of metal oxides and reducing metals that are selected to produce thermite reactions. The metal oxides and reducing metals are deposited into layers utilizing chemical or physical deposition, vacuum deposition, sputtering, mechanical rolling, or ball milling. Individual layers are typically about 10 nm to about 1000 nm thick. The alternating layers are then removed from the substrate and reduced in size. The resulting pieces are then mixed with a binder, and then shaped into reactive fragments. The reactive fragments are mixed with high explosive and placed inside a warhead. When the warhead strikes a target, the reactive fragments are preferably driven into the target before the reaction occurs. Ensuring that the reactive fragments are in fact driven into the target before the reaction occurs can be accomplished by constructing the alternating layers of metal oxides and reducing metals so that those having the highest reactivity are towards the interior of the energetic material, while those having a lower reactivity are on the periphery (the top or the bottom). Additionally, the speed of the reaction can be controlled by controlling the thickness of the metal oxide and reducing metal layers, with a greater number of thinner layers producing greater contact between the metal and metal oxide, and faster reaction rates. This use of thermite to enhance high explosives fails to disclose that a layered thermite structure, by itself, provides numerous advantages over the reactive fragments disclosed by this patent.
U.S. Pat. No. 7,886,668 discloses metal matrix composite energetic structures for use in munitions. The composite energetic structures are made by alternating layers of metal oxides and reducing metals that are selected to produce thermite reactions. The metal oxides and reducing metals are deposited into layers utilizing chemical or physical deposition, vacuum deposition, sputtering, mechanical rolling, or ball milling. Individual layers are typically about 10 nm to about 1000 nm thick. The alternating layers are then removed from the substrate and reduced in size. The resulting pieces are then mixed with a binder that is selected to increase the density of the overall mixture. This increased density increases the ballistic effectiveness of a munition in which the composite energetic material is placed. The reaction of the energetic material is delayed by constructing the alternating layers of metal oxides and reducing metals so that those having the highest reactivity are towards the interior of the energetic material, while those having a lower reactivity are on the periphery (the top or the bottom). Additionally, the speed of the reaction can be controlled by controlling the thickness of the metal oxide and reducing metal layers, with a greater number of thinner layers producing greater contact between the reducing metal and metal oxide, and faster reaction rates. This use of fragmented thermite material fails to provide the numerous advantages of retaining a layered structure of thermite material, as described below.
U.S. Pat. No. 7,998,290 discloses an enhanced blast explosive utilizing a composite explosive material having a high explosive as well as energetic material dispersed within the high explosive. The composite energetic structures are made by alternating layers of metal oxides and reducing metals that are selected to produce thermite reactions. The metal oxides and reducing metals are deposited into layers utilizing chemical or physical deposition, vacuum deposition, sputtering, mechanical rolling, or ball milling. Individual layers are typically about 10 nm to about 1000 nm thick. The alternating layers are then removed from the substrate and reduced in size. These reduced size pieces are mixed with the high explosive. The energetic material increases the overpressure duration of the blast, thereby increasing lethality for a given pressure level. The reaction of the energetic material is delayed by constructing the alternating layers of metal oxides and reducing metals so that those having the highest reactivity are towards the interior of the energetic material, while those having a lower reactivity are on the periphery (the top or the bottom). Additionally, the speed of the reaction can be controlled by controlling the thickness of the metal oxide and reducing metal layers, with a greater number of thinner layers producing greater contact between the metal and metal oxide, and faster reaction rates. This use of thermite to enhance high explosives fails to disclose that a layered thermite structure, by itself, provides numerous advantages over the reactive fragments disclosed by this patent.
US 2007/0169862 discloses an energetic thin-film initiator. At least one fuel layer and oxidizer layer are provided on a substrate. A pair of electrical conductors are connected to the structure to provide an electrical impulse. The resulting reaction ignites a secondary energetic material.
U.S. Pat. No. 6,712,917 discloses a hybrid inorganic/organic energetic composite made from metal inorganic salts, organic solvents, and organic polymers. Fuel metal powder is also included in the composition.
U.S. Pat. No. 6,679,960 discloses an energy dense explosive wherein particles of a reducing metal and a metal oxide are dispersed throughout a high explosive. The particle size and packing density are varied to control the blast characteristics. The reducing metal, metal oxide, and high explosive are suspended in a polymeric binder or matrix. The particles of reducing metal and metal oxide may be mechanically bonded prior to suspension in the polymer.
U.S. Pat. No. 4,875,948 discloses a combustible delay barrier that is intended to ignite upon intrusion, thereby delaying unauthorized entry until the arrival of authorities. The delay barrier includes a combustible layer having an oxidizer, a fuel metal, and a binder which also serves as a source of fuel.
U.S. Pat. No. 6,843,868 discloses a rocket propellant and explosive made from metal nanoparticles and fluoro-organo chemical compounds or fluoropolymers as microbeads, nanoparticles, or powder.
US 2007/0272112 discloses a reactive material for use in shot shells. The reactive material includes at least one binder, at least one fuel, and at least one oxidizer. The fuel and oxidizer may form a thermitic composition, having a metal and a metal oxide that react exothermically.
US 2010/0193093 discloses a process for preparing composite thermite particles. Within this process, a reducing metal and a complementary metal oxide are milled at a temperature of less than 50° C. The milling is performed within a ball mill. The temperature is lowered using liquid nitrogen or other liquefied gas. The result is repeated fracturing and stolid state welding of the metal and metal oxide, thereby forming layers of metal oxide and metal having an average thickness of between 10 nm and 1 μm. The resulting particles are less than 100 μm in size, and generally less than 10μ. These particles may be pressed together to form consolidated objects having dimensions of a few millimeters up to tens of centimeters. Pressing can be performed either at room temperature or at lower temperature. A fluidic binder may be added before or after pressing.
None of the above references disclose an energetic or thermite material wherein the reducing metal and metal oxide are deposited in layers, and then simply utilized in that layered configuration to produce an explosive shock. Furthermore, none of the above references discloses the use of multiple, individually controlled ignition points. Accordingly, there is a need for an energetic or thermite material having a layered structure and multiple ignition points. There is a further need for an ignition system providing individual control of multiple ignition points. This structure not only facilitates manufacture of an energetic or thermite material for numerous applications, but also facilitates other advantages such as charge and blast shaping, ignition timing, pressure curve control and maximization, safe neutralization of the energetic material, and other advantages that are more fully explained below.